1. Field of the Invention
The present invention relates to an apparatus, a method and a computer-readable recording medium for setting correction magnitudes of a signal transmitted via a signal transmission channel connecting each pair of a plurality of pairs of communication devices.
2. Description of the Related Art
Electronic devices such as information processing devices, transmitters and the like, that perform predetermined processes by receiving and outputting signals are generally built using a plurality of communication devices connected by a backboard (hereinafter, “BWB”). Each communication device that makes up the electronic device is normally realized by a printed board that includes circuits that receive and send signals and integrated circuits that perform predetermined processes. The backboard includes a plurality of slots for insertion of input terminals and output terminals of the communication devices. The slots are connected to each other through the wiring pattern, and the signals are exchanged among the communication devices through the slots.
FIG. 16 is a schematic drawing of the backboard. The backboard shown in FIG. 16 has eight slots (slots #1 to #8). Pairs of slots #1 and #2, slots #3 and #4, slots #5 and #6, and slots #7 and #8 are connected by the wiring pattern. Each pair of slots is shown to be connected by a single wiring pattern in FIG. 16. However, as the signals are transmitted in both directions between a pair of slots, there are two wiring patterns connecting each pair of slots.
With the increasing demand for higher processing speeds of electronic devices, it has become inevitable to transmit the signals at increased speeds. This has resulted in quality degradation (for example, degradation of bit error rate) of the transmission signals produced by the printed board and BWB. Transmission channel properties such as dielectric loss of the insulating material used in the printed board and BWB are attributable to the degradation of transmission signals.
Pre-emphasis is one of the methods for correcting degradation of the transmission signals, wherein signals are corrected when they are transmitted. Another method for correcting degradation is called equalizer, wherein signals are corrected when they are received.
FIGS. 17A to 17D are drawings of waveforms for explaining pre-emphasis. FIG. 17A is a drawing of a waveform determined on the transmitting side, and FIG. 17B is a drawing of a waveform determined at the receiving side in a case when the signals are transmitted without first correcting them. As can be seen from FIGS. 17A and 17B, when the signals are transmitted without first correcting them, the shoulder of the waveform falls on the receiving side due to the degradation of the quality of the transmission signals caused by the transmission channel properties. To counter this, as shown in FIG. 17C, the shoulder portion of the transmission signals on the transmission side is emphasized by the pre-emphasis. This results in correction of the waveform on the receiving side, as shown in FIG. 17D.
FIGS. 18A to 18D are drawings of waveforms for explaining equalizer. Similar to FIGS. 17A and 17B, FIGS. 18A and 18B are drawings of waveforms determined at the transmitting side and the receiving side, respectively, in the case when the signals are transmitted without first correcting them. In the equalizer method, the transmission signals received on the receiving side are emphasized at the shoulder portion. As a result, a corrected waveform is obtained on the receiving side, as shown in FIG. 18D.
Thus, the quality of the transmission signals can be corrected by subjecting the transmission signals to pre-emphasis (hereinafter, “PE”) on the transmitting side or equalizer (hereinafter, “EQ”) on the receiving side. However, the magnitudes by which the transmission signals are to be corrected (emphasized) need to be determined and set on the transmitting side and the receiving side.
The optimum magnitudes of correction (hereinafter, “correction magnitudes”) vary according to the length of the wiring pattern between two slots. This necessitates the maintenance person to determine the correction magnitudes that correspond to least error rate of the transmission signals by a tedious process of manually changing the PE and EQ correction magnitudes repeatedly and transmitting signals between the printed boards, and set the settings corresponding to the correction value on the receiving side and the transmitting side.
There are known technologies (for example, Japanese Patent Application Laid-open No. 2004-15622) for reducing the effort for determining the optimum setting value during initial settings of the electronic device, for example, by an automatic process of determining an optimum setting value by transmitting signals between the slots while automatically changing the setting values, and by setting the determined optimum setting value in the processing unit that performs the correction of the signals.
However, the BWBs in recent years have a full mesh topology wherein any two slots can be paired up. However, which two slots will be paired up depends on how the electronic device is to be used. Therefore, the maintenance person needs to determine the optimum setting values for the slots that will be paired up.
Applying the conventional technology to the BWB having a full mesh topology entails determining the optimum setting values for all the slot pairs, considerably increasing the time taken for the initial settings process.
Further, with prolonged use of the electronic device, the pattern impedance can change from the original value due to aging degradation or environmental changes, causing the quality of the signals transmitted between the slots of the printed board and BWB to deteriorate.
This necessitates once again determining the optimum PE and EQ setting values. Changing the PE and EQ setting values when the electronic device is running causes further degradation of the signals. As an alternative, the electronic device can be temporarily stopped to reconfigure the settings. However, stopping the electronic device will stop the task or the service the electronic device is used for in an affair, and if the number of slots on the BWB is large, the down time will be all the more longer, adversely affecting affair work.
There is a need to detect and set an optimum correction value for the signals in a short time.